CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
Learner’s Book
answers
Unit 1 Photosynthesis and the carbon cycle
Topic 1.1 Photosynthesis
Getting started
Learners should see that the plant that has light is
taller and greener than the one kept in the dark.
They may also see that leaves of the plant in the
light are broader and more numerous, and the stems
are thicker. Learners may remember that plants
make food by photosynthesis, and cannot do this
in the dark, so they do not have enough ‘food’ to
be able to grow well. They may also know that
chlorophyll is what makes plants look green, and
that this is used to absorb energy from light. With
no light, the plant does nto make chlorophyll.
Think like a scientist: Investigating
how light intensity affects the rate of
photosynthesis
1
This will depend on the results that learners
obtain. They are likely to find that the mean
number of bubbles is greatest when the lamp
is closest to the test tube.
2
Check that:
• the axes are the right way round, with
distance of lamp on the x-axis and mean
number of bubbles on the y-axis
• both axes are fully labelled, including units
• there are good scales on both axes
• the points are plotted neatly as small
crosses, in exactly the right places
• a neat line has been drawn; this could be a
best fit line, or learners could use a ruler to
join each point to the next.
3
decreases
4
increases
Questions
1
carbon dioxide and water
2
glucose and oxygen
3
Photosynthesis transfers energy from sunlight
into chemical energy in glucose. The plant
can use the glucose to make other substances.
When the grasshopper eats grass, it takes in
some of this energy. The lizard gets some of
the energy when it eats the grasshopper.
4
Plants release oxygen into the air when they
photosynthesise. Animals such as lizards need
oxygen for respiration.
Activity: Words beginning with photoEasy words include: photograph, photography,
photographer, photographing, photocopier,
photocopying and photocopy. A few learners may
also know photostat and photogenic. Other less
likely words for them to think of include photon,
photophobia, photocell and photofinish.
Think like a scientist: Collecting the gas
produced in photosynthesis
1
1
So that the gas could be collected over water.
2
So that the water plant could get energy for
photosynthesis.
Activity: Photosynthesis and respiration
Similarities: They are both chemical reactions.
They both happen inside cells. They both involve
energy changes (energy transfers). They both
involve glucose, oxygen, carbon dioxide and water.
Differences: Respiration happens in all living cells,
but photosynthesis only happens in some plant cells.
(Some learners may also know that photosynthesis
can happen in the cytoplasm in bacterial cells, but
this knowledge is not expected at this level.)
Respiration happens in cytoplasm and mitochondria,
but photosynthesis happens in chloroplasts.
Photosynthesis needs sunlight, but respiration
does not.
The reactants in respiration are the products in
photosynthesis, and vice versa.
In photosynthesis, energy from sunlight is
transferred to chemical energy in glucose.
In respiration, energy in glucose is released for the
cell to use.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
Topic 1.2 More about
photosynthesis
Getting started
1
in the green parts/in the leaves and stem
2
because they contain chlorophyll
3
because they are not green/do not receive light
Think like a scientist: Planning an
investigation into the effect of
fertilisers on plant growth
1
The hypothesis should state a predicted effect
that changing one variable has on another
variable. For example:
The more fertiliser the duckweed plants have,
the faster they will grow.
There are many other possible hypotheses.
Check that the hypothesis is genuinely testable
by experiment.
2
Answers will depend on the hypothesis being
tested. It is advisable to have at least five
different values of the variable.
3
Learners are likely to suggest counting the
number of leaves. They could either decide to
count each set of duckweed just once, after a
set period of time, or they could count each
one at regular intervals such as every two days.
4
This will depend on which variables are being
changed; any other variables that could affect
the rate of growth, such as light intensity and
temperature, should be kept the same.
5
This will depend on the learner’s experiment.
They are likely to need Petri dishes, some
duckweed plants, some fertiliser and a way of
measuring it, and a timer.
Questions
1
The carbon dioxide particles have kinetic energy.
They are in constant, random motion. By chance,
some of them will go into the leaf through the
stomata. Some will also come out. But, overall,
more will go in than out because there are more
of them outside the leaf than inside it.
2
Some of the oxygen diffuses out of the leaf.
Some of the oxygen is used in respiration.
3
Plants get their protein by using the
carbohydrates they make in photosynthesis
and adding nitrogen to them to make proteins.
Animals get their protein by feeding on plants
and/or other animals.
4
Nitrate and magnesium are both needed for
making chlorophyll, so a shortage of either
of them makes leaves go yellow. Nitrate is
also needed for making proteins, but without
magnesium the plant cannot photosynthesise,
so it has fewer carbohydrates to make proteins
from. A lack of either nitrate or magnesium
reduces growth.
Think like a scientist: Testing a leaf for
starch
1
a
b
2
This makes it easier to see the colour change
when iodine solution is added.
Starch is stored in the chloroplasts.
Boiling breaks down the cell membranes,
so the iodine can reach the starch.
6
There are few risks in this experiment.
Fertiliser should be handled with care, as it
would not be good for it to be ingested. Clean
up any spills quickly.
3
Most learners will get a positive test result,
showing that the leaf does contain starch. This
was produced from the glucose that was made
by photosynthesis in the chloroplasts.
7
The predictions should match the hypothesis.
4
Only the green parts contained starch. The
white parts have no chlorophyll, which is
needed to absorb energy from sunlight and
without which photosynthesis cannot happen.
Answers to questions 1 and 2 in part 2 will vary
from learner to learner.
Activity: Which surface of a leaf has
most stomata?
Learners should see more bubbles emerging from
the lower surface of the leaf because this is where
most stomata are.
2
The bubbles contain air. They are likely to
contain a lot of oxygen if the leaf has been
photosynthesising.
The warm water makes the gases inside the air
spaces in the leaf expand, which makes them come
out of the leaf.
Topic 1.3 The carbon cycle
Getting started
In carbon dioxide in the air, the carbon atom is part
of a compound; in photosynthesis it becomes part
of a glucose molecule, but is still a carbon atom.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
Tube F: Plant photosynthesises and respires,
but photosynthesises more than it respires,
and therefore uses up carbon dioxide.
Maggots respire, giving out carbon dioxide.
The two are likely to balance out.
Questions
1
a
b
2
3
The food chain should have a correct
sequence of organisms, with one plant
and three animals. Arrows should go in
the correct direction. For example:
fig tree → wasp → spider → lizard.
Yes, the arrows could also indicate how
carbon atoms are transferred. Carbon
is contained in the food that animals
eat, in the form of compounds such as
carbohydrates and proteins.
Proteins, carbohydrates and fats. Learners
could also suggest particular compounds, such
as haemoglobin. (Note that animals do not
contain starch.)
3
There would be no (or very little) combustion
of fossil fuels.
4
They take a very long time to form. We are
using them up much faster than they are being
replenished.
6
To make sure that having a platform in place
did not cause the differences between the
results in the different tubes.
Activity: Modelling the carbon cycle
1
No, in the real carbon cycle only some carbon
atoms will move at any one point in time.
Learners could suggest having only one or two
atoms moving on each occasion.
2
Learners should find that stopping
combustion results in fewer carbon atoms
ending up in the air.
Topic 1.4 Climate change
Questions
A 3; B 1; C 3; D2
Think like a scientist: How do plants
and animals affect carbon dioxide
concentration?
Questions
1
An asteroid is a rock, smaller than a planet,
which orbits the Sun.
1
Learners will probably find these results:
Tube A: yellow, high carbon dioxide
Tube B: purple, no carbon dioxide
Tube C: yellow, high carbon dioxide
Tube D: yellow, high carbon dioxide
Tube E: yellow, high carbon dioxide
Tube F: red, some carbon dioxide
2
2
Organisms were respiring in all the tubes.
It produced a lot of heat, which killed plants
and animals close to the collision site.
It produced a huge tsunami, which killed
plants and animals on land that were swamped
by sea water.
It sent dust high into the atmosphere, so plants
died because they could not photosynthesise.
Animals then died because there was no food
for them to eat.
3
Plants were photosynthesising in tubes B and F.
3
1.3 °C
4
a
b
4
The temperature fell by 0.3 °C between 1880 and
1910. It rose by 1.6 °C between 1910 and 2016.
5
5
Tube A: No photosynthesis because no light;
plant respires, giving out carbon dioxide.
Tube B: Plant photosynthesises and respires,
but photosynthesises more than it respires;
carbon dioxide is used up.
Tube C: Maggots respire, giving out carbon
dioxide.
Tube D: Maggots respire, giving out carbon
dioxide.
Tube E: No photosynthesis because no light;
plant respires, giving out carbon dioxide.
Maggots respire, giving out carbon dioxide.
Multiply the number of years until the end of
the century by 3 mm.
6
As the mean global temperature increases,
more land ice melts and adds extra water to
the oceans. Also, higher temperatures cause
sea water to expand.
Carbon dioxide would be used up in tube B.
Carbon dioxide would be given out in
tubes A, C, D and E.
Think like a scientist: How do rising
temperatures affect sea level?
1
Learners should find that melting ice on
land and increasing water temperature both
increase the water level. Melting ice in the sea
does not increase the water level.
2
They indicate how sea level is expected to rise.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
Activity: The carbon cycle and
climate change
Respiration and combustion increase the level of
carbon dioxide in the atmosphere. Photosynthesis
decreases it.
Learners could suggest:
• Plant more trees, because they will
photosynthesise and take carbon dioxide out of
the air.
• Stop deforestation (same reason).
• Stop burning fossil fuels, to reduce combustion.
• Stop using so much energy, so that we do not
need to use as much fuel.
Learners may also be aware of other issues not
covered here, such as eating less meat (because
production and transport of meat uses a lot of
energy and produces a lot of carbon dioxide) or
reducing air travel.
Check your progress
1.1 a
b
c
d
e
carbon dioxide
oxygen
soil
chlorophyll
stomata
1.2 a
b
the type of seaweed
Any three from: the temperature;
the light intensity; the size of the
piece of seaweed; the time for which
the apparatus is left.
the volume of gas collected (after a set
period of time).
c
1.3 a
b
4 tonnes per hectare
Adding more than 60 kg per ha gives
only a very small increase in yield. It is
likely that the cost of the extra fertiliser
would outweigh the small increase in
income from selling the grain.
c
The wheat plants use the nitrate to make
proteins. The proteins can be used to
make new cells, some of which will be
used to produce the grains.
d
In a different place, there might be a
different concentration of nitrate in the
soil before the fertiliser is added. There
might be a lack of other minerals in the
soil. The soil might be better or worse
at holding water. There might be more
shade in one place than another. The
temperature might be different.
e
Magnesium is needed for making
chlorophyll.
1.4 a i D
ii B
iii A
iv C
b i 3
ii 2
iii 1
c glucose, starch, carbohydrate, protein,
fat, cellulose or chlorophyll – allow any
other correct organic compound.
1.5 a Sea level will rise. There will be more
extreme weather events, such as
typhoons and hurricanes.
b iMany species of organisms are
completely destroyed.
ii Look for the idea of long-term
reduction in photosynthesis
because of dust thrown up into the
atmosphere, which reduces light
penetration.
This in turn reduces food for
animals.
Other reasons are the immediate
results of the impact, including
the heat and pressure wave in the
vicinity of the impact, and a
massive tsunami.
Unit 2 Properties of materials
Topic 2.1 Atomic structure and
the Periodic Table
Getting started
Answers will depend on what learners can recall.
You should use this as a form of assessment
for learning. Learners should manage to name
electrons, neutrons, protons and the nucleus. Some
4
may be able to give facts such as the charges on the
particles: protons – positive, neutrons – no charge
and electrons – negative. They may be able to
recall the relative masses of the particles: protons
and neutrons having more mass than electrons.
They may be able to recall the arrangement of the
particles as in the Rutherford model.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
Questions
9
1
6
2
4
10 Melting points increase as you go down
the group.
3
6
4
Diagram should have three shells, with
electrons structure 2:8:2, and a nucleus with
12p and 12n in the centre.
5
Aluminium
6
Diagram should have two shells, with electrons
structure 2,7, and a nucleus with 9p and 10n in
the centre.
7
The nucleus is made up of protons and
neutrons in both models. In the Rutherford
model, the electrons are all shown in one cloud
around the nucleus. In the model we use today,
the electrons are shown arranged in different
shells or energy levels around the nucleus. In
the model we use today, each shell can contain
up to a particular number of electrons.
Topic 2.2 Trends in groups within
the Periodic Table
Getting started
Metals in the same group as magnesium: beryllium
or calcium. (Accept other metals in this group if
you are using a full Periodic Table.)
Metals in the same period as magnesium: sodium
or aluminium.
Non-metallic solid in the same period as
magnesium: silicon, phosphorus or sulfur.
Gas in the same period as magnesium: chlorine
or argon.
Questions
5
1
The metals (except Aluminium) are found on
the left side of the table.
2
The boiling points decrease as you go down
the group.
3
It is lower than 777 °C.
4
eight more electrons
5
The size of the atoms increases as you go
down this group.
6
All have an outer shell containing one electron
and an inner shell containing two electrons.
7
This group of metals could be called Group 1
because there is one electron in the outer shell.
8
The atoms get larger and the reaction with
water gets more violent as the size of the atoms
increase.
non-metals
11 The colour gets darker as you go down
this group.
12 Boiling points increase as you go down
the group.
13 The melting point of iodine would be higher
than −7 °C and boiling point higher than 59 °C.
14 Iodine would be less reactive than bromine.
15 7
16 The size of the atoms increases as you go
down this group.
17 The atoms are similar in that they all have 7
electrons in their outer shell.
18 Because the atoms of each element has 7
electrons in its outer shell.
19 The melting points increase as you go down
this group.
20 The size of the atoms increases as you go
down this group.
21 The outer electron shells are all full and have
8 electrons (other than helium, which only has
2 electrons).
22 The atoms of each element have 8 electrons in
their outer shell.
23 The melting- and boiling points of krypton
will be higher than those of argon.
Think like a scientist: Observation of
the reactions of Group 1 metals with
water
1
These might include the use of safety glasses
and a safety screen; handling the metals with
forceps; using only a small piece of each
metal, and warning students about their
position in the room.
2
Descriptions should include any movement
across the water; change in the solid metal;
fizzing, any flame and colour of the flame.
3
lithium + water → lithium + hydrogen
hydroxide
sodium + water → sodium + hydrogen
hydroxide
potassium + water → potassium + hydrogen
hydroxide
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
4
This might include the reaction producing
heat; a gas is released, and the metal moves
around the water surface.
5
The differences may include the amount of
movement on the water and the intensity
of the violence of the reactions. Accept any
observed differences.
6
These may include the colour; the fact that
they are soft and can be cut; they are all light
and float on water and they react to form an
hydroxide with water. Accept any observed
similarities.
7
8
The reaction increases in intensity as you
go down Group 1. This would suggest that
rubidium reacts extremely violently and would
not be safe to use in schools.
When these Group 1 metals react with water,
they produce the alkalis lithium-, sodium- and
potassium hydroxide.
from the electrostatic charges between the
electrons and the protons.
9
Diagram of calcium atom should have four
shells, with electron structure 2,8,8,2, and a
nucleus.
Diagram of calcium ion should have three
shells, with electron structure 2,8,8, and a
nucleus. (Students may or may not write 2+ to
the top right of the calcium ion diagram.)
10 2
11 CaCl2
12 CaO
13 carbon dioxide, methane, water,
hydrogen chloride and ammonia.
14
Topic 2.3 Why elements react to
form compounds
Getting started
The learners’ drawings should match those in the
Learners’ Book in Topic 2.2. The point here is to
focus the learners on getting the details correct by
discussing their drawings with their partner.
Questions
16 methane CH4; carbon dioxide CO2; nitrogen N2
Topic 2.4 Simple and giant
structures
1
2,8,1
Getting started
2
2,8
3
Cl
4
Cl−
5
Diagram should have three shells, with
electron structure 2,8,8, and a nucleus.
6
Diagram should have two shells, with electron
structure 2,8, and a nucleus.
7
Potassium can lose an electron more easily
because the outer electron is a long way from
the nucleus and the positive electrostatic
charges on the protons, so it is easier for the
electron to escape from the potassium atom.
The outer electron in the lithium atom is
closer to the positive electrostatic forces, so it
is more difficult for it to escape.
Learners should be able to describe the structure
of sodium and chlorine atoms. They might be able
to discuss the stability of the two atoms. They
should be able to describe the formation of the
ions of these two elements and the formation of
an ionic bond between them. Suitable diagrams
such as those shown in Topic 2.2 could be drawn.
This should not be used simply as a right/wrong
answer but the idea is to provoke discussion
between learners to help them improve their
understanding.
8
6
15 An ionic compound, because the compound is
formed from a metal and a non-metal.
Fluorine is more reactive than chlorine
because it can gain an electron more easily
because the outer shell of electrons is further
Questions
1
An ionic bond is formed when atoms lose or
gain an electron (or electrons) but a covalent
bond is formed when atoms share electrons.
2
ionic bond
3
A molecule is the name given to a particle
with more than one atom where the atoms
share at least one electron in a covalent bond.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
4
A macromolecule is a giant molecule. Examples
are silicon dioxide, diamond or graphite.
5
Ionic, because it has high melting- and boiling
points and it is a compound formed from a
metal and a non-metal.
6
A simple molecule with covalent bonds. It has
low melting- and boiling points. Also credit
the fact that it is formed from two non-metals
so must have covalent bonds.
7
A gas
8
They have high melting points because they
are ionic compounds. The electrostatic forces
between the ions in these compounds are very
strong so, in order to melt the solids, a great
deal of energy is need to break these bonds.
9
They are composed of simple molecules; the
forces within the molecules are strong, but the
forces between the molecules are weak, so less
energy is needed to melt them.
10 Copper sulfate has ionic bonds. It has formed
a giant structure of crystals and is made from
a metal and a a non-metal.
11 This substance has ionic bonds because it has
very high melting- and boiling points.
12 Silicon dioxide is hard and has a very high
melting point; these are not properties that
are expected of a substance with covalent
bonds. We know that silicon dioxide must have
covalent bonds because it is formed from two
non-metals so the only explanation can be that
silicon dioxide has a giant covalent structure.
Think like a scientist: Ionic compounds
conducting electricity
7
1
The expected answer would be yes, but credit
answers based on the learner’s findings.
2
When ionic compounds dissolve in water, the
ions are free to move about in the solution
and can carry the electric charge and so the
solution can conduct the electricity.
3
The expected answer would be no, but credit
answers where learners may have found some
conduction if they are based on their results.
4
The ions are held in a strong lattice so they
are not free to move to carry the charge and
conduct electricity. Learners should explain any
conduction they did observe, for example the
electrodes were touching or the crystal was wet.
5
If a covalent substance were used, there would
be no conduction of electricity because the
forces inside the molecules are strong and
there are no charged particles to carry the
electricity.
Check your progress
2.1 a
b
c
d
e
f
g
2.2 a
b
c
2.3 a
b
c
d
e
Below 180 °C and above 63 °C
Below 883 °C and above 688 °C
hydrogen
More bubbles of gas and more heat will
be generated than with lithium, but less
than with potassium.
Lithium 7; sodium 23; potassium 39;
rubidium 85
The number of protons plus the number
of neutrons.
Diagram should have a nucleus, three
shells, and the electron structure 2,8,1.
Diagram should be the same as in the
question, but with one additional
cross in the outer shell.
A fluorine ion is more stable than a
fluorine atom because the outer (highest
energy level) shell of electrons is full.
F−
ionic
covalent
covalent
ionic
ionic
2.4 CH4
2.5 a
b
The strong electrostatic forces between
the positive sodium ions and the
negative chlorine ions.
The melting- and boiling points of
sodium chloride will be high because
the electrostatic forces are strong.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
Unit 3 Forces and energy
Topic 3.1 Density
7
a
Getting started
8
The gas must be less dense than air; the gas
must have a density low enough so that the
average density of the balloon, the string and
the gas is less than that of air.
9
It is cooler at those times, so the surrounding
air will be denser; the difference in density
between the balloon and the surrounding air
will be greater; the balloon will float more
easily.
1
the (3-dimensional) space occupied by an
object / length × width × height of an object
2
1 kg feathers
3
1 cm of iron
3
Questions
1
a pine wood
b i polycarbonate
ii
The density of polycarbonate is
greater than the density of water.
2
mass
_______
a​​
b
c
3
a
b
c
Activity: Densities of some
regular objects
1
Those objects with calculated densities greater
than 1.0 g/cm3 should be predictedto sink;
those that are less, to float.
2
If the balance is not at zero, then the
(recorded / measured) mass of the object will
be too large or too small.
3
a
There is material missing from the
corners, so if measured to where the
corner should be, then the calculated
volume will be too large.
b
The mass should be correct because
damage to the object will not affect the
reading on the balance.
c
If the calculated volume is too small, then
the density value will be too large / vice
versa; if the recorded mass is too small
then the density value will be too small /
vice versa.
​​
volume
mass
13.5
density = _______
​​
​​ = ____
​​   ​​ = 2.7 g/cm3
5
volume
It will sink because its density is greater
than that of water.
4 × 3 × 6 = 72 cm3
mass
54
density = _______
​​
​​ = ___
​​   ​​ = 0.75 g/cm3
volume 72
It will float because its density is less than
that of water.
mass
10 300
density = _______
​​
​​ = ______
​​
​​ = 1030 g/cm3
10
volume
b iThe material will float because its
density is less than that of sea water.
ii
The material will sink because its density
is greater than that of pure water.
4
a
5
a
mass
density = _______
​​
​​
volume
Think like a scientist: Densities of some
irregular objects
so mass = density × volume
1
The volume is read correctly from the bottom
of the meniscus.
2
Either: place a heavier object of known
volume on top to make the less dense object
sink, measure the total volume of the two
objects by displacement, subtract the volume
of the denser object.
Or: tie a denser object with string to the less
dense object, submerge them both in water,
measure the total volume of the two objects
by displacement, subtract the volume of the
denser object and the string (that can also be
measured by displacement).
6
mass
_______
mass
_______
​​
​​ so volume = ​​
volume
density
4.5
volume = ​​ ____ ​​ = 0.50 cm3
8.96
a
78 − 50 = 28 cm3
mass
84
density = _______
​​
​​ = ___
​​   ​​ = 3 g/cm3
volume 28
Any two from: plastic is less dense than
steel / the result from part b is the average
density of all the materials / the toy is
hollow OR contains air.
b
c
8
= 8.96 × 20 = 179.2 g
b
A = kerosene; B = water; C = mercury
density = ​​
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Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
3
4
Use a larger container filled to the very top,
submerge object, collect water that overflows,
measure the volume of the water collected
using several measuring cylinders.
The result is likely to be anomalous because
wood floats on water, therefore the density of
wood is expected to be less than the density of
water, which is 1.0 g/cm3.
Topic 3.2 Heat and temperature
Getting started
1
2
Any heat source, such as a flame, a hot plate
or an immersion heater; it is also acceptable
to add more water that is at a higher
temperature.
a
The water in the swimming pool.
b
The temperature increases are the same,
so the larger mass of water requires more
thermal energy.
Questions
1
a
b
J
°C
2
a
b
The temperatures are the same.
The thermal energy in the larger block,
B, is greater, so B has more heat.
a
Thermal energy contained within that
object; the total energy of all the particles
in the object.
The average energy of the particles in
an object.
3
b
4
A → B and A → C and B → C
5
The statement will be true only if the
substances are the same and have the same
mass or same number of particles. It is
possible for an object with a small mass to
have a higher temperature than an object with
larger mass, yet the object with larger mass
may have more thermal energy, so has more
heat.
Activity: The Mpemba effect
9
1
The table should have a column for starting
temperature of the water in °C (normally be
on the left). There should be a column for
time taken to freeze in minutes or seconds, or
minutes and seconds.
2
Each temperature difference correctly
calculated by subtracting −18 °C from each
temperature.
3
The greater the temperature difference, the
greater the rate of thermal energy transfer.
4
The trend in the learner’s result is correctly
described; this should be a trend rather than
only quoting results.
Think like a scientist: Measuring heat
and temperature
1
The table should have a column for energy in
joules and a column for temperature in °C.
2
The graph should be drawn with linear scales
and cover half the grid in both directions.
Ideally, the graph should be a straight line.
3
As the energy supplied to the water increases,
the temperature of the water increases.
4
Any three from: volume or mass of water
/ type of container / starting temperature
of the water / same temperature increase /
same quantity of thermal energy from the
immersion heater.
5
Any three from: transferred to the cup / to
the air above the water / to the surface below
the cup / to evaporate some of the water / to
the area around the top of the heater (if the
heater was not completely submerged).
6
Any three from: insulation around the cup /
insulation under the cup / ensure the heater is
completely submerged (if it was not) / put a lid
on the cup.
Topic 3.3 Conservation of energy
Getting started
1
Most should be able to recall at least some
from: kinetic, chemical, gravitational
potential, elastic potential, electrical, thermal.
2
For example, chemical can be changed to
electrical in a cell or battery.
3
Where energy spreads out and becomes
less useful.
Questions
1
a
2
a
b
Energy cannot be created or destroyed;
energy can be changed or transferred
(statements can be in either order).
b i false
ii false
iii true
1000 − 500 = 500 J
100 − 80 = 20 J
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2021.
This material
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andJones,
is subject
to Fellowes-Freeman
further changes prior
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Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
c
1300 + 700 = 2000 J
3
a
b
100 − 70 = 30%
55 + 10 = 65; 100 − 65 = 35%
4
Sofia is not correct. The useful energy output
and the wasted energy cannot add up to more
than the energy input. 12 + 7 = 19 J, whereas
energy input is 18 J. So 18 − 7 = 11 J of the
electrical energy is changed to light.
Activity: Conservation of energy
1
2
3
3
The temperature will increase; the
surroundings are at a higher temperature than
the ice cream; thermal energy will move from
the surroundings to the ice cream.
4
Zara is correct; heat, or thermal energy,
moves but cold does not move, and the gloves
keep the cold air from contacting the skin;
the gloves keep the heat of the hands from
escaping to the colder surroundings.
5
a
The first bottle swings through a smaller
distance as the second bottle swings through
a greater distance. The second bottle then
swings through a smaller distance as the first
bottle swings through a greater distance. The
cycle repeats.
b
The water is at lower temperature / is
colder than the engine; thermal energy
from the engine moves to the water; heat
from the engine is dissipated into the water.
Thermal energy from the water is
dissipated into the air around the radiator
(or dissipated into the radiator); the air
at the front of the radiator is at lower
temperature than the water.
Kinetic energy from one bottle is transferred
to the other bottle. Energy cannot be gained
(as no additional energy is input), so as one
bottle swings more, the other must swing less.
Activity: Hot coffee
1
method B
Energy is used to overcome friction and air
resistance; energy is dissipated.
2
Adding the cold milk to the coffee lowers the
temperature of the coffee.
This lowers the temperature difference
between the coffee and the surroundings.
The rate of thermal energy transfer (and
therefore cooling) is lower when the
temperature difference is lower.
3
Same cups; same volume (or mass) of coffee;
same volume (or mass) of milk; same starting
temperature of coffee; same temperature of
milk; same room temperature; same exposure
to draughts / moving air.
Activity: Bottle racers
1
the (twisted) elastic band
2
elastic potential
3
kinetic
4
The bottle racer moves faster / further
(depending on their observation) as there is
more elastic potential energy to change to
kinetic energy.
Topic 3.4 Moving from hot
to cold
Think like a scientist: Temperature
change from heat dissipation
Getting started
1
Thermal energy from the room is transferred out
through the open window; cold air may enter the
room but thermal energy moves from the warm air
into the cold air.
Table should have a column for time in
seconds or minutes and a column for
temperature of water in °C.
2
Axes should be scaled in a linear way with
temperature on the y-axis.
Line graph should be drawn either with a best
fit straight line or a smooth curve.
3
The results may show a lag before temperature
starts to increase and may also show a
decrease in rate of temperature change as time
progresses. Learners should describe the trend
shown in their graph.
4
The temperature of the water will stop
increasing either when the lamp is switched
off or when the water reaches the same
temperature as the lamp.
Questions
1
Thermal energy moves from warmer / hotter /
higher temperature places to cooler / colder /
lower temperature places.
2
a
b
The temperature will decrease.
The food is at a higher temperature than
the surroundings; thermal energy will
move from the food to the surroundings;
heat will be dissipated from the food.
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Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
10
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
5
The temperature increase of the water will be
slower with the LED; the water will not reach
as high a temperature with the LED as it did
with the lamp.
Topic 3.5 Ways of transferring
thermal energy
Getting started
1
a
b
c
2
a
b
c
In a solid, the particles are regularly
arranged and in contact.
In a liquid, the particles are randomly
arranged and in contact.
In a gas, the particles are randomly
arranged and not in contact.
Particles vibrate more vigorously, taking
up more space; the solid expands.
Particles vibrate more vigorously, taking
up more space; the liquid expands.
Particles move faster and collide with each
other and the walls with more force; the
gas expands.
a
b
c
conduction, convection and radiation
conduction and convection; both of these
methods require particle movement and
there are no particles in a vacuum.
Conduction because the particles in
a solid are close together/touching to
transfer the energy from vibrations;
convection cannot occur in a solid
because the particles are not free to move.
2
The black T-shirt will absorb thermal radiation
faster, so Arun will feel hotter sooner. The
white T-shirt will reflect more thermal
radiation, so Marcus will feel cooler for longer.
3
a
b
conduction
radiation
4
a
The electric heater gets hot (changes
electrical energy to thermal energy), heat
is transferred from the heater to the water
by conduction, particles in water around
the heater vibrate more vigorously and
take up more space, water around the
heater expands and becomes less dense,
this hotter water floats to the top of the
tank, cooler water moves to the bottom
of the heater to replace the water that has
risen; this sets up a convection current
that heats all the water.
Because of convection; hotter water will
be at the top, hotter water is less dense
and will float / rise above cooler water
(which will be at the bottom).
c
Higher up than the first heater; because
of convection, the water below the heater
will not be heated.
Think like a scientist: Conduction of
thermal energy in different materials
The risk assessment should include keeping paper
away from the flame; not touching the hot metal rod;
making sure the candle will not fall over, and allowing
everything to cool at the end of the investigation.
1
Thickness / diameter of rod; distance of rod
from flame; mass of wax; distances between
paperclips; mass of paperclips.
2
This will vary according to available
equipment and design of the investigation.
3
The paperclips closer to the heat source should
fall first, some of the more distant paperclips
may not fall within the allocated time. If
different materials have been used, then some
comparison should be made. For example,
the paperclips started to fall off faster from a
copper rod than from an iron rod.
4
The heat source makes particles in the rod
vibrate more vigorously; the vibration is
transferred to neighbouring particles by
collisions; this carries on along the rod; if
different materials have been used then a
comparison should be made – for example, the
vibrations are transfered faster in the copper
than in the iron; transferring thermal energy
along the rod, the wax is heated by conduction
from the rod and will melt when it reaches
its melting point; particles in the solid wax
vibrate more vigorously until they can move
further apart and turn to a liquid.
5
Some materials such as wood will burn; other
materials such as plastic will melt.
Questions
1
b
Activity: Observing convection
1
The drawings should, at the very least, show
arrows for the direction of the convection
current. Arrows should point up from the heat
source (which is clearly shown at one side of
the base of the beaker), then across the upper
part of the water, then down the other side
and back across the bottom to the heat source.
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Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
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Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
11
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
2
Explanations should refer to particles
vibrating more vigorously due to being
heated. These particles then take up more
space, expanding the liquid, decreasing the
density of the heated liquid and this heated
liquid, floating or rising through the denser
surrounding liquid.
Think like a scientist: Emitting thermal
energy by radiation
e.g., every 1 minute (details of the cans need
not be given as question asks about these cans,
i.e., the ones that were used in the first part of
the investigation).
Topic 3.6 Cooling by evaporation
Getting started
1
In evaporation, some particles have sufficient
energy to leave the surface of the liquid
and enter the gas state, so evaporation
only occurs at the surface. In boiling, all
particles have sufficient energy to turn to
gas, so boiling occurs at all positions in the
liquid at once. Evaporation can occur at any
temperature whereas boiling only occurs at
one temperature.
Particles in a liquid all have different energies.
Those at the surface that have sufficient energy
can leave the liquid and enter the gas state.
1
The prediction should be that the water in the
cans will cool at different rates and that this
is linked to the colours; the black can should
cool quickest and the shiny silver can should
cool slowest. This should be linked to the
relative ability of each colour to emit thermal
radiation.
2
The table should have one column (at the
left) for time in minutes, or in minutes and
seconds. There should then be columns for the
temperature in °C for each colour.
2
3
The graph should have temperature on the
y-axis and time on the x-axis. All three (or
more) lines should be drawn on the same grid;
each line should be clearly identified using a
key for the colour of the can. The lines should
be curves if the results have been recorded
correctly.
1
4
The trend for all cans should be described as
the temperature decreasing with time. More
detail can be added, such as the decrease in
temperature was faster at the start / when the
water was hotter. A comparison should be
made between the rates of cooling of each
colour of can.
The energies of the particles in water at 25 °C
are different.
Particles with the least energy stay in the liquid.
Particles with the most energy can leave the
liquid.
When liquid water turns to gas, the water is
said to evaporate.
2
C
3
a
5
The answer should link the original prediction
with the observations.
6
Reference to the graph; any point that are
further from the line or does not appear to
fit with the others.
7
8
Questions
b
4
Volume (or mass) of water in each can;
material / type of can; starting temperature
of water; location of cans; none stirred or
shaken.
Use of a radiant heat source or placing in
direct sunlight; if a radiant heater is used then
all cans to be equal distance from the heat
source; same volume of water in each; water at
same starting temperature in each; cans left for
the same time; temperature measured at equal
regular intervals which should be specified,
a
b
5
The average energy of the particles
decreases because the particles with more /
the most energy leave the liquid; slower
moving particles are left behind in the
liquid.
The temperature decreases; temperature
is the average energy of the particles in
a substance, so as the average energy
decreases, the temperature decreases.
Evaporation causes cooling; thermal
energy from skin is used to evaporate
the sweat.
There is no loss of thermal energy due to
evaporation.
When isopropanol contacts the skin, the liquid
evaporates; evaporation lowers the average
energy of the particles in the liquid, so the
temperature of the liquid decreases; thermal
energy from the skin is used to evaporate the
liquid.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
12
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
Think like a scientist: Making an air
cooler
1
2
3
Thermal energy from your hand will affect the
thermometer reading / the thermometer will
measure the temperature of your hand rather
than the temperature of the air. (Answer
should be specific and not just refer to getting
better results.)
There should not be a significant difference
between the temperatures measured in steps
2 and 3. This is because the air has not
been heated or cooled; the only difference is
movement. The temperature from step 7 should
be lower; this is because the water from the
towel has evaporated, lowering its temperature.
Thermal energy from the air around the wet
towel is used to evaporate the water.
The three temperatures from steps 2, 3 and 7
should be the same if a dry towel is used; this
is because there is no cooling by evaporation.
3.2 B and D
60
3.3 a​​ ___ ​​= 1.2 g/cm3
50
b It will sink because its density is greater
than that of water.
3.4 a
b
3.5 a
b
°C or degrees Celsius
J or joules
3.6 a
Energy is always conserved, meaning that
energy cannot be created or destroyed.
3.7 50 − 5 = 45 J
3.8 a
Activity: Feeling the effects of
evaporation
1
To increase the rate of evaporation.
2
The alcohol should feel coldest, the water next
and the soap the least cold. Blowing makes
each of the liquids (perhaps with the exception
of the soap) feel even colder.
3
a
b
alcohol
soap
4
There are no numerical results / no measurements.
5
Either repeat the experiment using a skin
thermometer or perform an experiment
similar to that in Main Teaching Activity How
does sweating work.
Check your progress
3.1 B
The average energy is the same because
the temperatures are the same.
The heat in beaker Y is greater because
there are more particles (with the same
average energy) / the total energy of all
the particles is greater.
b
The temperature of the ball decreases
because thermal energy is transferred to
the water. The temperature of the water
increases because thermal energy is
transferred from the ball.
C
3.9 conduction; thermal energy is transferred
from the tea to the spoon; metal is a good
conductor of heat
3.10 a
b
air is heated; the air becomes less dense;
the air floats / rises
air cools; the air becomes denser; the air
sinks / falls
3.11 the black car is hotter inside; black is a
good absorber of radiation; white is a good
reflector / poor absorber of radiation
3.12 evaporation; thermal energy is removed from
the skin; the most energetic particles leave
the sweat, lowering the average energy of the
remaining particles
Unit 4 Maintaining life
4.1 Plants and water
Questions
1
The long extension from the cell increases its
surface area. This increases the surface across
which it can take up water and mineral salts,
so this uptake happens faster.
2
Nitrate ions are needed to make proteins.
Magnesium ions are needed to make chlorophyll.
Think like a scientist: Investigating
transport in a celery stalk
1
The drawing should show an outline of the
cut stalk, and coloured spots in the correct
positions. This will depend on the type of
stalk that has been used in the experiment.
2
xylem cells
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Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
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Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
13
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
3
a
b
4
To make sure that the coloured areas in
the stalk had appeared because dye had
been carried up through the stalk, not
leaked in from the side.
To remove any dye from the outside of
the stalk, so we could be sure that the
coloured spots were caused only by dye
that had been carried up the stalk.
The water would move from the soil into the
root hairs, then across the root to its centre.
There it would enter the xylem vessels, which
carry it up through the stalk.
Think like a scientist:
Planning an experiment
Questions
Questions
1
The parts are identified in the diagram in
Topic 1.2.
2
The upper surface is covered with a layer of
wax that stops water passing through. The
underside has stomata, which are openings
leading to the air spaces inside a leaf. Water
vapour can diffuse out from the air spaces,
through the stomata.
Think like a scientist:
Investigating transpiration
1
Whether the leaves were exposed to the air
or not.
2
The soil was covered in both. Learners should
also have tried to keep the temperature the same
for both plants and to use two plants of the
same size. They should have ensured there was
the same quantity of water in the soil in each pot
and that the light intensity was the same.
1
The water will move up faster, because higher
temperatures give more kinetic energy to
particles.
2
As temperature increases, the speed at which
water moves up the stem increases.
3
The plan should include the idea of changing
the temperature, and measuring how fast
the dye moves up the stem at different
temperatures.
Answers will depend on the learners’ results.
They are likely to find that the loss of mass
was much greater in the plant that did not
have a bag covering its leaves.
4
Water vapour was lost from the leaves of the
plant that did not have its leaves covered, by
transpiration. The water vapour that was lost
from the leaves of the other plant was trapped
inside the bag and could not escape.
3
4
The apparatus is likely to include a container,
some coloured water, several stalks, a timer and
a ruler. Learners may need other apparatus or
materials, depending on their plan.
The independent variable is temperature.
The dependent variable is the rate at which
the coloured water moves up the stalk. This
involves measuring time and distance.
Variables to keep the same include depth
of coloured water, size of the stalk and
light intensity.
Risk assessment: Cutting the stalk carries a
risk of harm from the sharp blade. Cut on
a firm, non-slip surface and move the blade
away from the body.
4.2 Transpiration
Getting started
The particles in the liquid should be randomly
arranged, but with each particle touching at least
two other particles. The particles in the gas should
not be touching at all, and should be far apart.
When liquid water turns to a gas, the particles
move faster and spread further apart.
Think like a scientist: Which side of a
leaf loses most water?
1
This will depend on the learners’ results. The
most likely sequence (in increasing ability to
conserve water) is: leaf with no petroleum jelly;
with petroleum jelly on upper surface only;
with petroleum jelly on lower surface only; with
petroleum jelly on both surfaces.
2
The upper surface has few (or no) stomata, but
the underside has stomata, through which water
vapour can diffuse out from the air spaces.
3
It is unlikely that the two leaves would lose
exactly the same mass. The leaves were
probably different masses to start with and
contained different quantities of water. One
leaf may have been in a slightly draughtier
place than another. Learners may make other
suggestions, depending on what happened in
their experiment.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
14
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
4
5
Using two leaves gives more reliable results, as
you can avoid the possibility that the one leaf
you test might be unusual. Using even more
leaves would be much better, as this would
then give you the opportunity to identify
any anomalous results. It would increase the
likelihood of obtaining reliable data.
1
oxygen and any nutrients, such as water,
glucose, vitamins, minerals
2
carbon dioxide and urea
3
Vitamin A for good vision for the mother and
the fetus, and for their white blood cells to
fight pathogens.
Vitamin C for strong skin and blood vessels
for both the mother and the fetus.
Vitamin D for strong bones and teeth for both
the mother and the fetus.
4
protein: meat, fish, pulses, milk and other
dairy products
carbohydrate: bread, rice, potatoes, pasta,
cereal grains
iron: meat, dark green vegetables, fish and
shellfish, nuts and seeds
calcium: dairy products, nuts and seeds
vitamin A: green vegetables, carrots, squash,
fruit, dairy products, fish
vitamin C: citrus fruits, potatoes, colourful
berries
vitamin D: oily fish
This will depend on the learners’ experiences as
they did their experiment. Do not give credit to
answers that involving changing another variable.
Activity: Conserving water in
the desert
Answers will vary, depending on the desert
plants studied in Stage 8, and each learner’s own
experience. Possible suggestions could include:
small leaves with a thick layer of wax to reduce
transpiration; very deep or wide-spreading roots to
increase access to water.
4.3 Excretion in humans
Getting started
1
Yes; they both need water for transport and
cooling.
2
We also need water for getting rid of waste
materials in urine.
3
Plants use water for support and
photosynthesis.
Questions
1
renal system
2
Carbon dioxide diffuses into the blood and is
carried to the lungs. There, it diffuses from the
blood capillaries into the alveoli. It is removed
from the body in expired air.
3
Questions
Plants make their own proteins, using
carbohydrates that they have made in
photosynthesis and nitrates that they absorb
from the soil. So they are unlikely to have
excess proteins that they need to get rid of.
4.4 Keeping a fetus healthy
Getting started
Description of the nutrients and their functions
are detailed in Stage 8, Topic 7.1. Learners
may suggest a range of ideas about particular
requirements in the diet of a pregnant woman;
accept all at this stage, and perhaps ask learners to
revisit them when they have carried out the activity
in Topic 4.4: Display about diet during pregnancy.
Check your progress
4.1 a
b
c
d
e
f
kidney
ureter
urea
bladder
urethra
urine
4.2 Plants take up water from the soil into their
root hairs.
The water flows through xylem vessels which
carry it to the plant’s leaves.
In the leaves, a lot of the water changes from
liquid to gas.
It diffuses out of the leaf through the
stomata.
4.3 a
b
c
d
e
balance
3g
945 − 808 = 137 g.
137 ÷ 6 = 22.8 g
From the plant. The plant with no
covering over either the plant or the soil
lost a total of 137 g, whereas the plant
with the plant covered lost a total of 31 g.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
15
CAMBRIDGE LOWER SECONDARY SCIENCE 9: TEACHER’S RESOURCE
f
4.4 a
b
Water vapour diffused out of the leaves
of the plant, through its stomata. The
water vapour condensed to a liquid on
the inside surface of the bag.
c
There is a wide range of correct answers.
Credit any answer that includes a correct
function of that nutrient. For example:
She needs more protein because protein
is needed for growth, and the fetus is
growing.
She needs more calcium to help the fetus
form strong bones and teeth, as well as
keeping her own bones and teeth strong
and healthy.
She needs more iron so that the fetus can
produce haemoglobin for its red blood
cells, as well as increasing the number of
her own red blood cells.
d
Accept any correct responses. For
example, fish for protein; yoghurt for
calcium; meat for iron.
Most people’s diets contain more fat
than they need, so her normal diet is
likely to contain enough fat for herself
and her fetus. Too much fat can lead to
obesity and heart disease.
Any two of: Carbon monoxide from
the cigarette smoke gets into the fetus’s
blood and reduces how much oxygen
it can carry. Nicotine also gets into the
fetus’s blood; it is an addictive substance
and can damage the blood vessels.
Babies born to mothers who smoke
during pregnancy are at increased risk of
having a low birthweight.
Unit 5 Reactivity
Topic 5.1 Reactivity and
displacement reactions
5
magnesium + oxygen → magnesium oxide
6
zinc
Getting started
7
yes
The point of this task is to provoke discussion
rather than to focus on right or wrong answers.
Learners may recall colour changes, new products
such as gases being formed, changes in pH when
chemical reactions take place. They should be
able to discuss relevant examples from their
previous experience such as reactions of Group 1
metals with water, burning magnesium ribbon or
neutralisation reactions.
8
magnesium
9
no
Questions
1
a
b
2
a
b
Lithium should be placed below sodium
and above calcium.
Lithium reacts with water more vigorously
than calcium but less vigorously than
sodium.
Platinum should be placed below gold.
Credit a plausible position, such as near
gold.
Platinum is very unreactive, it does not
react with oxygen at all (it does not
tarnish).
3
Metal B is the most reactive. You can tell
because the most bubbles are given off.
4
zinc + sulfuric acid → zinc sulfate + hydrogen
Think like a scientist: Displacing metals
1
If there has been a change in the colour of the
solution or the metal, that would show that
one metal had displaced another.
2
This will depend on what you have been able
to provide, but it is likely to be magnesium.
3
This will depend on what you have been able
to provide, but it is likely to be copper.
Topic 5.2 Using the reactivity
series and displacement reactions
Think like a scientist: Identifying
a mystery metal – planning the
investigation
Credit: a logical plan that includes basic
observations of the metal burning in air, with
water and with dilute acid; displacement reactions;
an equipment list; safety considerations; a way
of recording results; an indication of what might
be expected in each observation/test and how this
would help to identify the metal.
Original material © Cambridge University
Press
2021.
This material
is not
andJones,
is subject
to Fellowes-Freeman
further changes prior
to publication.
Cambridge
Lower
Secondary
Science
9 final
– Mary
Diane
& Michael
Smyth
© Cambridge University Press 2021
16